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Based Off of What?

I recently received this e-mail from a colleague: “I’m losing my mind reading papers with the expression based off of, which has become very widely used (rather than based on). What do you know about where it came from and how its meaning emerged?”

The answer to her question, at the time I received the e-mail, was “very little.” I too had noticed the construction and had the sense it was on the rise. A search of Google Books with the Ngram Viewer confirmed my suspicion:

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The rise in use since 1980 is dramatic, but the numbers are still very small. In Google Books, which captures written prose, the construction “based on” outnumbered “based off of” by about 100,000:1 in the year 2000, when the Ngram graph ends. And as the figure below shows, “based on” has been on the rise in English since the mid 19th century.

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The numbers in the Corpus of Contemporary American English (COCA) also show “based on” as the super-super-majority form in formal prose: “based on” appears 29,677 times in academic writing; “based off of” appears in academic writing only once (from 1990 to the present). According to COCA, “based off of” is seven times more likely to occur in speech than in academic writing. But remember that COCA has only one occurrence of “based off of” in the academic register, so the ratio is literally 7 occurrences in speech to just the one in academic writing. As I said, the numbers for “based off of” are very small.

The use of prepositions in English is notoriously idiomatic. When is it “a story of” versus “a story about”? Why is it “as a result” and not “in a result” or “for a result”? (It is, after all, “in conclusion” and “for a reason.”) And prepositions in (fairly) fixed phrases can change over time—for example, the newer “on accident” is competing with “by accident” right now.

With “based on” one could argue that because things are physically built on bases, it makes more sense to say “based on.” I agree: That is perfectly logical. But language isn’t always logical, and once “based on” becomes as much or more metaphorical than literal, it doesn’t seem surprising to me that the preposition might shift—especially given that one can metaphorically “build off” things.

My intuition is that “based off” sounds more informal, as do many other “off” expressions (e.g., “going off what she said” or “borrow off someone”). That “based off” might sometimes become “based off of” aligns it with the other constructions that now sometimes use “off of”—a compound preposition that the American Heritage Dictionary notes “is generally regarded as informal and is best avoided in formal speech and writing.”

A quick search of COCA shows “off of” occurring much more often in speech than in written prose, but it does appear in academic writing: for example, “elevated off of the chest wall” and “a terracotta arm broken off of a larger statue.” The one example of “based off of” comes from the academic journal Exceptional Children: “For our study, the parameters used in the simulation were based off of values derived from a large empirical data set.”

A Google search for “based off of” doesn’t turn up a lot of prescription on it yet, although there is some. I have mentioned the construction to a few colleagues, and it’s clear at least some of them are circling it in student writing. “Based off of” watchers will want to follow the emerging prescription to understand the future of this construction. If the phrase, either as “based off” or “based off of,” finds a comfortable home in our speech, then it will be prescriptivism that determines whether and/or how quickly it can make the jump to academic writing. Stay tuned—this one is hard to call.

Update: If you extend the search with the Google Books Ngram Viewer through 2008, you see that “based off of” continues to rise, just about tripling in use from 2000 to 2008. The construction “based on” rises slightly or stays steady from 2000 to 2004 and then takes a small dip in frequency from 2004 to 2008. By 2008, the ratio of “based on” to “based off of” is closer to 10,000:1.

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